The present invention is directed to a method and device for removing oxygen from oils and fats. The dissolved oxygen is removed from the oils and fats for the purposes of retarding oxidation deterioration, rancidity, gum formation, etc.
The term "oil" is applied to a large variety of substances which differ greatly in chemical nature. However, these substances may be classified by their type and function as follows:
a. Fixed oils--fatty substances of vegetable and animal organisms--contain esters (usually glycerol esters) or fatty acids. PA1 b. Volatile or essential oils--odorous principles of vegetable organisms--contain terpenes, camphors, and related compounds. PA1 c. Mineral oils, fuel oils and lubricants--hydrocarbons derived from petroleum and its products. PA1 1. Yeast, fungal cells, algae and protozoa, having mitochondrial membranes containing an electron transfer system which reduces oxygen to water, are grown under suitable conditions of active aeration and a temperature which is conducive to the growth of the cells, usually about 20.degree. C. to 45.degree. C. in a broth media. Alternately, mitochondria may be obtained from cells of animal or plant origin. PA1 2. The cells are collected by centrifugation or filtration, and are washed with distilled water. PA1 3. For the preparation of crude mitochondrial membrane fragments, a concentrated suspension of the cells is treated to break up the cell walls and mitochondria. This is accomplished by known means, for example, by ultrasonic treatment or by passing the suspension several times through a French pressure cell at 20,000 psi. PA1 4. The cellular debris is removed by low speed centrifugation or by microfiltration (cross-flow filtration). PA1 5. The supernatant or filtrate is subjected to high speed centrifugation (175,000.times.g at 5.degree. C.) or ultrafiltration. PA1 6. For the preparation of material of higher purity, the cells of step 2 are suspended in a buffer containing 1.0M sucrose and are treated by means which break up the cell walls or membranes but leave the mitochondria intact. This is accomplished by known means, for example, by ultrasonic treatment, passage through a French pressure cell at low pressure, enzymatic digestion or high speed blending with glass beads. PA1 7. The cellular debris from step 6 is removed by differential centrifugation or filtration. PA1 8. The supernatant or retentate from step 7 is passed through a French Press at 20,000 psi to break the mitochondria into small pieces. PA1 9. Mitochondria debris from step 7 is PA1 10. The supernatant or filtrate from step 9 is subjected to high speed centrifugation (175,000.times.g at 5.degree. C.) or ultrafiltration. PA1 11. The pellet or retentate from step 5 (crude mitochondrial fragments) or the pellet or retentate from step 10 (purified mitochondrial membrane fragments) are resuspended in a buffer solution at a pH of about 7.0 to about 7.5. A preferred buffer solution is 0.02M solution of N-2-hydroxyethylpiperazine-N-2-ethane sulfonic acid (HEPES). PA1 12. The membrane fragments in the buffer solution are then passed under pressure through a filter having openings of about 0.2 microns. PA1 13. The suspension is then stored at about -20.degree. C. for later use or it may be freeze dried.
Fixed oils are the non-volatile, fatty oils characteristic of vegetables and animals, as opposed to the volatile essential oils of flowers and plants which are readily vaporized by heat. In this regard, fixed oils absorb oxygen and become resinous (drying oils) or remain liquid (non-drying oils) while the essential oils evaporate.
Fixed oils are fatty compounds consisting primarily of triesters or esters of glycerol with fatty acids and are commonly referred to as "triglycerides" or simply "glycerides". A glyceride may be called either a fat or an oil depending upon its melting point and physical consistency at room temperature. In this regard, oils derived from animals, plant seeds or nuts are identical with their respective fats with the exception that the fats are solids and the oils are liquids at room or ambient temperature. However, this distinction is somewhat illusionary in that slight changes in temperature may cause many glycerides to change from liquids to solids or from solids to liquids.
The chemical and physical properties of fixed oils and fats, also known as lipids, vary widely depending to a large extent upon the type of fatty acids in the glyceride. However, in almost all of the commercially important glycerides, the fatty acids are straight chain and contain an even number of carbon atoms. Along this line, the majority of fixed oils and fats are made up of fatty acids of more than 16 carbon atoms.
Fixed oils and fats may be produced from a wide variety of sources including plant, animal, and marine sources. Fixed oils and fats from plant sources, such as vegetable oils, are obtained by pressing or extracting the oils from the seeds, nuts, or fruit pulp of various plants, such as soybean, cottonseed, corn, peanut, sunflower, safflower, olive, rapeseed, sesame, coconut, palm, etc. In seeds, the oil or fat, which is concentrated in the kernel, varies greatly in amount, i.e. soybean (18-22%), peanut (46-50%), and safflower (46-54%). The two main sources for oil from fruit pulp are palms (30-55%) and olive (38-50%). Fixed oils and fats from plant sources have varying degrees of saturation.
Fixed oils from animal sources are produced by rendering (i.e. heating the fatty tissue with steam, hot water, or other solvents to melt the glyceride, followed by separating the oil or glyceride from the water or solvent) the fatty tissue (lard, tallow, etc.) of animals, such as cattle, pigs, poultry, and sheep. In addition, butter fat is an animal fat produced from milk. Fixed oils from marine sources are obtained from fatty tissue (tallow, lard) of whales, herring, etc. by rendering processes similar to those utilized in obtaining fixed oils from animals. Examples of marine oils include fish oils, fish liver oils, sperm oil, etc.
Once the crude fats and oils are extracted from the plant, animal or marine sources, the fats and oils may be utilized in their raw state or they may be further processed and converted to more valuable products. Along this line, the crude fats and oils may be refined to remove various gums, pigments, etc. in the oils, as well as bleached and/or deodorized to produce a uniformed product. Further processing, such as hydrolysis or hydrogenation, may occur to produce many different functional fats such as margarines or shortening.
Fixed oils and fats have a wide variety of commercial uses and exhibit both food and non-food applications. For example, there are both edible and non-edible vegetable oils. Oils such as soybean, sunflower, rapeseed, sesame, and safflower oils, are used predominantly in food processing and food stuffs, while technical and industrial oils, such as castorseed and tung oils, are used in non-food applications. Some oils, such as linseed and olive oil, can be utilized for both food and non-food applications. Examples of some of the primary uses of edible oils are margarine, hydrogenated shortenings, salad and cooking oils, frying oils, food shortening, mayonnaise, salad dressing, filled dairy products, bakery and cake mixes, and non-dairy products. The principle industrial uses of non-edible oils include paints, varnishes, soaps, detergents, plastic additives, and lubricants.
Furthermore, fixed oils and fats may be classified depending upon their "drying" characteristics. The drying of oils refers to the polymerization of the glycerides of unsaturated oils induced by exposure to oxygen In this regard, fixed oils and fats may be classified as drying (linseed, tung), semi-drying (soybean, cottonseed), and non-drying oils (castor, coconut). Drying oils are those which upon exposure to air or oxygen form an elastic film These oils, such as linseed or tung oil, are utilized mainly in paints and varnishes Non-drying oils are those which remain permanently "wet" or "oily" such as olive or castor oil. Semi-drying oils are those which remain "somewhat wet" such as soybean, cottonseed, or corn oil Semi-dry oils are used frequently in cooking and in various food products.
As indicated above, fats and oils may be characterized depending upon their relative volatility. Along this line, "fixed oils" are non-volatile oils which become resinous (drying oils) or remain liquid (non-drying oils) upon exposure to oxygen or heat while "essential oils" are volatile oils which are readily vaporized by heat or the exposure to oxygen or air. Thus, essential or volatile oils are classified separately from fixed or non-volatile oils.
More particularly, essential oils are any of the odoriferous oily products which are distillable from plants. Essential oils are distinguished from "fixed" or fatty oils by their volatility, non-greasiness, and non-saponifying properties Essential oils exist in plants, specifically in the oil sacs found in the leaves (patchouli), twigs (clove stems), blossoms (rose), fruit (mandarin), bark (cinnamon), roots (ginger), buds (cloves), berries (pimenta), seed (caraway), gum (myrrh), balsam (tolu balsam), etc. of a wide variety of plants. As such, essential oils produce the characteristic odor of the flowers, leaves, roots, etc. of plants. These plants are processed by comminution, and the action of heat, water, and solvents to yield their essential oils. The essential oils may then be utilized as flavor and/or fragrance agents in various food products and beverages, cosmetics, perfumes, etc.
Examples of the commercially available essential oils include allspice (pimenta berry), bitter almond, amyris, anise, star anise, sweet basil, bay (myrcia), bergamot, sweet birch, bois de rose (rosewood), camphor, cananga, caraway, cardamom, cassia, cedarwood, cinnamon, citronella, clove, coriander, eucalyptus, geranium, ginger, grapefruit, jasmine, juniper, labdanum, lavandin, lavender, lemon, distilled lime, japanese mint, neroil, nutmeg, ocotea, bitter orange, sweet orange, origanum, orris root, palmarosa, patchouli, black pepper, peppermint, petitgrain, bigarade, pine, pinus pumilio, rose, rosemary, dalmation sage, sage clary (sage muscatel), East Indian sandalwood (santal), spearmint, spike lavender (spike), thuja (cedarleaf), thyme, turpentine, vetiver, wintergreen, and ylang ylang.
While fixed and/or essential oils and fats may be processed through various refinement steps such as filtration, deodorization, bleaching, etc., several forms of deterioration, such as oxidation and hydrolytic rancidity, can occur over time. As a result, various unwanted flavors and odors may develop. For example, soybean oil can develop a disagreeable fishy flavor or beef fat can become tallow. Hence, oxidative and hydrolytic rancidity in fixed and/or essential oils and fats is a serious flavor and odor defect and is highly objectionable.
In this regard, it is well known that the presence of oxygen in products containing oils and fats can cause a great deal of detrimental damage. For example, the off-flavors developed in lard, vegetable oils, hydrogenated shortenings, crackers, biscuits, breakfast cereals, dry cake mixes, and essentially all foods that incorporate lipids are produced by oxidation. Similarly, oxidation is usually associated with the spoilage of dried whole milk, cream, butter, and butter oil. In addition, many essential oils became darker and thicker upon exposure to air.
The changes which occur in fixed and/or essential oils and fats over time including changes in color, consistency, and odor. This is reportedly due to the formation of hydroperoxides which then decompose to form aldehydes which have a disagreeable odor and flavor. Since these changes in fixed and/or essential oils and fats greatly decrease the product's marketability, it is desirable to reduce the presence of oxygen in the overall product.
In addition, it is also desirous to remove oxygen from various commercial or industrial fixed oils and fats. This is particularly true in non-edible vegetable oils used in paints and varnishes, wherein the presence of oxygen can create undesirable by-products, such as gum formation, etc.
Various packaging products, devices, processes, and chemical agents (i.e. antioxidants) have been developed over the years to retard the damage produced by oxidation of fixed and/or essential oils and fats. For example, oxidation retardation may be brought about by using opaque air-tight containers, or the nitrogen blanketing of clear glass bottles may be used. In addition, various deoxygenating devices including vacuum systems, oxygen-purging apparatuses, etc. are used to extract the oxygen. However, vacuum dereators and gas flushing apparatuses are fairly expensive and they do not necessarily reduce the dissolved oxygen content to an acceptable level. Moreover, these apparatuses have some drawbacks in that lubricants used therein sometimes find their way into the oils and fats being treated. The inclusion of even a small amount of such harmful agents within oils and fats utilized in beverage and/or food products can produce undesirable color and/or flavor changes in the overall product, as well as toxic effects.
Furthermore, various chemical agents, i.e. antioxidants, can be added to the fixed and/or essential oils and fats to retard oxidation and associated deterioration. Along this line, chemical antioxidants are required in animal fats since the animal fats contain no natural antioxidant materials. Although vegetable oils contain some nature antioxidants such as tocopherols (vitamin E active), tocopherols are not synthesized by mammals and occur in their fats only through the ingestion of plant materials and vegetable oils.
In addition, while vegetable oils contain some natural antioxidants, these antioxidants are often insufficient for even a relatively short period of time. Additional chemical antioxidants can be added to the fats and oils, however, with the exception of tertiary butyl hydroquinone (TBHQ), these chemical antioxidants are not very effective in oils and fats. Moreover, the consuming public is becoming increasingly more concerned about the uses of chemicals and preservatives in foods including antioxidants. Thus, a great deal of research is currently being undertaken in order to develop not only more universal, but also safer, antioxidants.
Chemical antioxidants are compounds added to various materials for the purposes of retarding oxidation and associated deterioration. They may be utilized alone or in combination with deoxygenating processes such as those indicated above. Chemical antioxidants operate by binding with specific intermediate free radicals (i.e. peroxy radicals) produced during oxidation degradation. By binding with the intermediate free radicals, the free radicals are incapable of propagating the chain reaction to decompose into other harmful free radicals. As a result, by binding with the intermediate reactant, antioxidants effectively inhibit the oxidation degradation reaction. A more detailed explanation concerning the operating mechanism of antioxidants may be found in Van Nostrand Reinhold Encyclopedia of Chemistry, Fourth Edition, 1984.
However, the use of antioxidants in foods, pharmaceuticals, and animal feeds, as direct additives is closely regulated. Along this line, when used in foods, chemical antioxidants are regulated to extremely low percentages by the Food and Drug Administration (FDA). Although antioxidants have been utilized for several decades and occur naturally in some food substances, intensive research continues in order to develop universal non-toxic antioxidants.
In this regard, the desirable properties of antioxidants, particularly when used in food products, may be summarized as indicated by Van Nostrand Reinhold, supra, by the following characteristics: (1) effectiveness at low concentrations; (2) compatibility with the substrate; (3) non-toxicity to consumers; (4) stability in terms of conditions encountered in processing and storage, including temperature, radiation, pH, etc.; (5) non-volatility and non-extractability under the conditions of use; (6) ease and safety in handling; (7) freedom from off-flavors, off-odors, and off-colors that might be imparted to the food products; and (8) cost effectiveness. As a result, antioxidants vary greatly depending upon such factors as the composition of the substrates, pH, temperature, processing conditions, impurities etc.
Accordingly, the present invention is directed to a method and device for continuously removing oxygen from fixed and/or essential oils and fats in a safe and efficient manner. The method and composition of the present invention may be utilized as an antioxidant in industrial oils and fats such as paints and varnishes, as well as food products, without altering the desired properties of the products produced thereby. The method and device of the invention fulfill the desired properties of an effective antioxidant as indicated above.